An apparatus and method for determining a temperature in a system having an object, an optical sensor, and a gas flow passing between the object and the optical sensor, sensing, with the optical sensor, a wavelength emitted from the object and indicative of an attenuation, sensing, with the optical sensor, a wavelength emitted from the object and indicative of a temperature of at least one of the object or the gas; and calculating a temperature of the gas using the wavelengths.